Burn down SwiftLint advisory violations from 109 to 4 (#1362)

Mechanical style fixes across the enabled rule set, mostly via
swiftlint --fix (trailing_comma, comma, colon, trailing_newline,
comment_spacing, unused_closure_parameter, unneeded_break_in_switch,
opening_brace) plus hand fixes:

- non_optional_string_data_conversion (45): .data(using: .utf8)! and
  ?? Data() fallbacks replaced with the non-optional Data(_.utf8),
  including two production sites (NIP-44 HKDF info constant and the
  announce canonicalization context/nickname bytes — byte-identical
  output, only the impossible-nil handling is gone).
- switch_case_alignment: LocationChannel had a misindented closing
  brace; also repaired an --fix artifact in BLEService's .none case.
- redundant_string_enum_value: TrustLevel raw values equal to the case
  names (encoded form unchanged).
- unused_optional_binding: let _ = binds replaced with != nil / is Bool.
- static_over_final_class: PreviewView.layerClass.
- Resolved the BinaryProtocolTests TODO by documenting that 8-byte
  recipient ID truncation is the fixed wire-field size, not a bug.

The 4 remaining violations are all todo markers for a shared
test-helpers module (tracked in #1088) and one Reuse note.

Co-authored-by: jack <jackjackbits@users.noreply.github.com>
Co-authored-by: Claude Fable 5 <noreply@anthropic.com>

localPackages/Arti/Package.swift

@@ -5,16 +5,16 @@ let package = Package(
     name: "Tor",  // Keep name "Tor" for drop-in compatibility
     platforms: [
         .iOS(.v16),
-        .macOS(.v13),
+        .macOS(.v13)
     ],
     products: [
         .library(
             name: "Tor",
             targets: ["Tor"]
-        ),
+        )
     ],
     dependencies: [
-        .package(path: "../BitLogger"),
+        .package(path: "../BitLogger")
     ],
     targets: [
         // Main Swift target
@@ -22,19 +22,19 @@ let package = Package(
             name: "Tor",
             dependencies: [
                 "arti",
-                .product(name: "BitLogger", package: "BitLogger"),
+                .product(name: "BitLogger", package: "BitLogger")
             ],
             path: "Sources",
             exclude: ["C"],
             sources: [
                 "TorManager.swift",
                 "TorURLSession.swift",
-                "TorNotifications.swift",
+                "TorNotifications.swift"
             ],
             linkerSettings: [
                 .linkedLibrary("resolv"),
                 .linkedLibrary("z"),
-                .linkedLibrary("sqlite3"),
+                .linkedLibrary("sqlite3")
             ]
         ),
         // Binary framework containing the Rust static library.
@@ -42,6 +42,6 @@ let package = Package(
         .binaryTarget(
             name: "arti",
             path: "Frameworks/arti.xcframework"
-        ),
+        )
     ]
 )